docs: def list(cls, datacenter=None):
          """List virtual machine vlan
  
          (in the future it should also handle PaaS vlan)."""
          options = {}
          if datacenter:
              datacenter_id = int(Datacenter.usable_id(datacenter))
              options['datacenter_id'] = datacenter_id
  
          return cls.call('hosting.vlan.list', options)